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Topic: Library for DS1307 Real Time Clock (Read 39 times) previous topic - next topic

mattt

Oct 01, 2007, 05:24 am Last Edit: Oct 01, 2007, 05:30 am by mattt Reason: 1
Hi all,

I'm new to Arduino, AVR, microcontrollers, and not proficient with C.
Here is my attempt at a library for the DS1307 real-time clock, which connect via I2C.

It covers the basics of stopping and starting the clock, setting (some validation) and read time components.

It does depend on the Wire lib.

Here's how I use it.
Code: [Select]

include <Wire.h>
#include <DS1307.h>

int rtc[7];  

void setup()
{
 Serial.begin(9600);
 /*
 RTC.stop();
 RTC.set(DS1307_SEC,1);
 RTC.set(DS1307_MIN,23);
 RTC.set(DS1307_HR,12);
 RTC.set(DS1307_DOW,1);
 RTC.set(DS1307_DATE,1);
 RTC.set(DS1307_MTH,10);
 RTC.set(DS1307_YR,7);
 RTC.start();
 */
}

void loop()
{
 RTC.get(rtc,true);

 for(int i=0; i<7; i++)
 {
   Serial.print(rtc[i]);
   Serial.print(" ");
 }
 Serial.println();

 delay(1000);

}



mattt

Here's the header file.
Code: [Select]
/*
 DS1307.h - library for DS1307 rtc
*/

// ensure this library description is only included once
#ifndef DS1307_h
#define DS1307_h

// include types & constants of Wiring core API
#include <WConstants.h>

// include types & constants of Wire ic2 lib
#include <../Wire/Wire.h>

#define DS1307_SEC 0
#define DS1307_MIN 1
#define DS1307_HR 2
#define DS1307_DOW 3
#define DS1307_DATE 4
#define DS1307_MTH 5
#define DS1307_YR 6

#define DS1307_BASE_YR 2000

#define DS1307_CTRL_ID B1101000  //DS1307

// Define register bit masks  
#define DS1307_CLOCKHALT B10000000

#define DS1307_LO_BCD  B00001111
#define DS1307_HI_BCD  B11110000

#define DS1307_HI_SEC  B01110000
#define DS1307_HI_MIN  B01110000
#define DS1307_HI_HR   B00110000
#define DS1307_LO_DOW  B00000111
#define DS1307_HI_DATE B00110000
#define DS1307_HI_MTH  B00110000
#define DS1307_HI_YR   B11110000

// library interface description
class DS1307
{
 // user-accessible "public" interface
 public:
   DS1307();
   void get(int *, boolean);
   int get(int, boolean);
     void set(int, int);
   void start(void);
   void stop(void);

 // library-accessible "private" interface
 private:
   byte rtc_bcd[7]; // used prior to read/set ds1307 registers;
     void read(void);
     void save(void);
};

extern DS1307 RTC;

#endif

mattt

Here's the cpp

Code: [Select]
extern "C" {
#include <../Wire/Wire.h>
}
#include "DS1307.h"

DS1307::DS1307()
{
 Wire.begin();
}

DS1307 RTC=DS1307();

// PRIVATE FUNCTIONS

// Aquire data from the RTC chip in BCD format
// refresh the buffer
void DS1307::read(void)
{
 // use the Wire lib to connect to tho rtc
 // reset the resgiter pointer to zero
 Wire.beginTransmission(DS1307_CTRL_ID);
   Wire.send(0x00);
 Wire.endTransmission();

 // request the 7 bytes of data    (secs, min, hr, dow, date. mth, yr)
 Wire.requestFrom(DS1307_CTRL_ID, 7);
 for(int i=0; i<7; i++)
 {
   // store data in raw bcd format
   rtc_bcd[i]=Wire.receive();
 }
}

// update the data on the IC from the bcd formatted data in the buffer
void DS1307::save(void)
{
 Wire.beginTransmission(DS1307_CTRL_ID);
 Wire.send(0x00); // reset register pointer
 for(int i=0; i<7; i++)
 {
   Wire.send(rtc_bcd[i]);
 }
 Wire.endTransmission();
}


// PUBLIC FUNCTIONS
void DS1307::get(int *rtc, boolean refresh)   // Aquire data from buffer and convert to int, refresh buffer if required
{
 if(refresh) read();
 for(int i=0;i<7;i++)  // cycle through each component, create array of data
 {
     rtc[i]=get(i, 0);
 }
}

int DS1307::get(int c, boolean refresh)  // aquire individual RTC item from buffer, return as int, refresh buffer if required
{
 if(refresh) read();
 int v=-1;
 switch(c)
 {
 case DS1307_SEC:
   v=(10*((rtc_bcd[DS1307_SEC] & DS1307_HI_SEC)>>4))+(rtc_bcd[DS1307_SEC] & DS1307_LO_BCD);
     break;
 case DS1307_MIN:
   v=(10*((rtc_bcd[DS1307_MIN] & DS1307_HI_MIN)>>4))+(rtc_bcd[DS1307_MIN] & DS1307_LO_BCD);
     break;
 case DS1307_HR:
   v=(10*((rtc_bcd[DS1307_HR] & DS1307_HI_HR)>>4))+(rtc_bcd[DS1307_HR] & DS1307_LO_BCD);
     break;
 case DS1307_DOW:
   v=rtc_bcd[DS1307_DOW] & DS1307_LO_DOW;
     break;
 case DS1307_DATE:
   v=(10*((rtc_bcd[DS1307_DATE] & DS1307_HI_DATE)>>4))+(rtc_bcd[DS1307_DATE] & DS1307_LO_BCD);
     break;
 case DS1307_MTH:
   v=(10*((rtc_bcd[DS1307_MTH] & DS1307_HI_MTH)>>4))+(rtc_bcd[DS1307_MTH] & DS1307_LO_BCD);
     break;
 case DS1307_YR:
   v=(10*((rtc_bcd[DS1307_YR] & DS1307_HI_YR)>>4))+(rtc_bcd[DS1307_YR] & DS1307_LO_BCD)+DS1307_BASE_YR;
     break;
 } // end switch
 return v;
}

void DS1307::set(int c, int v)  // Update buffer, then update the chip
{
 switch(c)
 {
 case DS1307_SEC:
   if(v<60 && v>-1)
   {
     //preserve existing clock state (running/stopped)
     int state=rtc_bcd[DS1307_SEC] & DS1307_CLOCKHALT;
     rtc_bcd[DS1307_SEC]=state | ((v / 10)<<4) + (v % 10);
   }
   break;
 case DS1307_MIN:
   if(v<60 && v>-1)
   {
     rtc_bcd[DS1307_MIN]=((v / 10)<<4) + (v % 10);
   }
   break;
 case DS1307_HR:
 // TODO : AM/PM  12HR/24HR
   if(v<24 && v>-1)
   {
     rtc_bcd[DS1307_HR]=((v / 10)<<4) + (v % 10);
   }
   break;
 case DS1307_DOW:
   if(v<8 && v>-1)
   {
     rtc_bcd[DS1307_DOW]=v;
   }
   break;
 case DS1307_DATE:
   if(v<31 && v>-1)
   {
     rtc_bcd[DS1307_DATE]=((v / 10)<<4) + (v % 10);
   }
   break;
 case DS1307_MTH:
   if(v<13 && v>-1)
   {
     rtc_bcd[DS1307_MTH]=((v / 10)<<4) + (v % 10);
   }
   break;
 case DS1307_YR:
   if(v<13 && v>-1)
   {
     rtc_bcd[DS1307_YR]=((v / 10)<<4) + (v % 10);
   }
   break;
 } // end switch
 save();
}

void DS1307::stop(void)
{
     // set the ClockHalt bit high to stop the rtc
     // this bit is part of the seconds byte
   rtc_bcd[DS1307_SEC]=rtc_bcd[DS1307_SEC] | DS1307_CLOCKHALT;
   save();
}

void DS1307::start(void)
{
     // unset the ClockHalt bit to start the rtc
     // TODO : preserve existing seconds
   rtc_bcd[DS1307_SEC]=0;
     save();
}




mattt

I'd really appreciate some feedback, especially around how I've a approached the BDC manipulations.

Thanks

xSmurf

I like it :) I've adapted the library for use with the DS1337 RTC. One issue I have with time setting is that it's hard to set the time wrong a source of epoch (serial, ntp).
"Pilots believe in a clean living... they never drink wisky from a dirty glass."

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